1. Field of the Invention
The present invention relates to a digital broadcast reception apparatus.
2. Description of Related Art
The subchannels included in the broadcast data of digital broadcasts are classified into free view channels and paid channels, and generally the video data and the audio data of the paid subchannels are encoded (hereinafter referred to as scrambled) so that only viewers who pay viewing fees can view the subchannel. Because the broadcast data includes mixed data of a non-scrambled subchannel and a scrambled subchannel, if an arbitrary subchannel is tuned, the scrambled subchannels that cannot be viewed are frequently tuned. Accordingly, for example, a digital broadcast reception apparatus detecting whether broadcast data is scrambled or not to perform channel up/down tuning has been known (see, for example, Japanese Patent Application Laid-Open Publication No. Hei 5-168019).
Moreover, an analog broadcast reception apparatus judging whether broadcast data is scrambled or not by detecting information about whether the broadcast data is scrambled or not, that is included in the vertical blanking interval (VBI) of the broadcast data of an analog broadcast, has been also known (see, for example, Japanese Patent Application Laid-Open Publication No. Hei 9-64847).
Moreover, an analog broadcast reception apparatus descrambling broadcast data using a key pulse included in the VBI of the broadcast data of an analog broadcast has been also known (see, for example, Japanese Patent Application Laid-Open Publication No. Hei 6-153195).
Moreover, a scramble apparatus which scrambles a packet after judging the necessity of the scrambling based on a packet identifier (PID) for identifying each packet included in broadcast data in a digital broadcast has been also known (see, for example, Japanese Patent Application Laid-Open Publication No. 2004-363976).
Now, as the scramble judgment methods for judging whether broadcast data of a digital broadcast is scrambled or not, for example, the following methods have been known:
(a) a method of judging broadcast data is scrambled when an MPEG-2 sequence header cannot be obtained within a predetermined time (for example, 10 seconds) from the start of the decode of video data,
(b) a method of judging broadcast data is scrambled when a value other than 0x0 is described in transport_scrambling_control bits in the TS packet headers of both or any of the video data and the audio data of a subchannel,
(c) a method of judging broadcast data is scrambled when a value other than 0x0 is described in PES_scrambling_control bits in the MPEG-2 Packetized Elementary Stream (PES) packets of both or any of the video data and the audio data of a subchannel,
(d) a method of judging broadcast data is scrambled when a CA_descriptor exists in the first descriptor description loop of a subchannel, and
(e) a method of judging broadcast data is scrambled when the CA_descriptor exists in the second descriptor description loop of a subchannel.
However, the scramble judgment method (a) is actually to start decoding and to judge success/unsuccess of the decoding, and consequently has a problem of taking too much time for the scramble judgment. Moreover, if any of the scramble judgment methods (b)-(e) is adopted as the scramble judgment method, there has been a problem that whether scrambled or non-scrambled cannot be judged accurately because the method to describe the information about whether scrambled or non-scrambled among (b)-(e) is different according to a broadcasting station or region.